The great helm enclosed the head and face, becoming one of the most recognizable helmets of crusader and high medieval knightly warfare.
The great helm is the fully enclosed cylindrical helmet of the thirteenth and fourteenth centuries — a flat-topped drum of riveted plates covering the entire head, pierced by a horizontal sight slit and a scatter of breathing holes.
It is the most complete head protection of the medieval period and the most punishing to wear. It closes the face entirely, which is the whole point, and it does so at severe cost to vision, hearing, breathing and heat, which is why its battlefield life is shorter than its fame suggests.
It is also the helmet that made heraldry necessary. A man inside a great helm is unidentifiable, so the crest on top and the arms on his shield and surcoat stop being ornament and become the practical means by which he is known.
The helm is built from several plates — typically a crown, a face plate and one or two side or rear plates — riveted together with the seams overlapped for strength. The flat top of the earlier forms is easy to make but poor at deflecting; later helms are given a rounded or conical crown for exactly that reason.
The face carries a horizontal ocularium, the sight slit, often reinforced with a raised band across the eyes, and below it clusters of pierced holes for breath. The distribution of those holes is usually asymmetric, more numerous on the side away from an opponent's lance, which shows how carefully the piece was thought through.
It was never worn alone. Beneath it went a padded arming cap and a mail coif, and by the fourteenth century a close-fitting steel cervelliere or bascinet as well, so that the great helm was the outer layer of a system rather than a single object. Much of its weight rested on the shoulders rather than the head.
The great helm exists for one tactical moment: the mounted charge with a couched lance, where a point arrives at the face at the combined speed of two horses. Against that, an open helmet is inadequate and a closed drum is not excessive.
It was worn in general battle through the thirteenth century, and helms of this family were in use at the Battle of Bouvines in 1214 and across the crusading campaigns of the period. Its decline in the field begins when the compromise becomes unattractive — when the same protection can be had without the blindness.
It kept a long second life in the tournament, where the charge is the whole event, the fight is brief, and restricted vision matters far less than in an all-day battle. Tournament helms grew heavier and more specialised long after field helms had moved on.
Its strength is completeness. Nothing else in the thirteenth century closes the face so thoroughly, and against the lance point and the descending sword it is very effective indeed.
Its limitations are severe and were understood at the time. Vision is reduced to a slit, peripheral sight is gone, hearing is muffled, and the interior becomes intensely hot; accounts of men suffocating or collapsing from heat in enclosed helmets are a recurring feature of the sources.
It was therefore often not worn until it was needed. Fighting men carried the helm at the saddle or had it carried for them, donning it before contact and removing it as soon as the press broke — a practice that is itself evidence of how uncomfortable the thing was.
The type grows out of the nasal helmet through the later twelfth century, as cheek and face plates extend across an open skull until the face is closed. The intermediate enclosed helms of about 1200 are recognisably the same object mid-evolution.
It reaches its classic flat-topped form in the first half of the thirteenth century, then rounds and lengthens through the century, with the crown becoming conical and the lower edge extending toward the shoulders.
In the fourteenth century it is displaced in the field by the bascinet, which offers a visor that can be raised, and retreats to the tournament and to funerary display. By the time of the Battle of Crécy in 1346 the bascinet is the fighting helmet and the great helm is increasingly ceremonial.
Surviving great helms are rare and mostly of German and Central European origin. The helm of Albert von Prankh in the Kunsthistorisches Museum in Vienna, of about 1300, is among the best known, and survives with the elaborate crest that would have identified its wearer.
The helm of Hans Rieter von Kornburg in the Germanisches Nationalmuseum in Nuremberg, of the mid-fourteenth century, retains its gilt decorative bands and a mail curtain at the lower edge — a reminder that these were decorated objects rather than bare steel drums.
Many surviving helms are funerary. Hung above a tomb as part of a heraldic achievement, they escaped the recycling that consumed working armour, which means the surviving sample is biased toward the ceremonial and the wealthy.